The role of suspension systems in motor vehicles is two fold; they serve to isolate the passengers from the irregularities of the road surface, and they also contribute to the control of the vehicle through managing the relative position of the tires to the vehicle body during vehicle operation. Suspension systems must perform these two functions over a variety of operating conditions, including steering, braking, and accelerating.
The term “independent suspension” refers to suspension systems which allow wheels on the same axle to move independently, that is, to react individually to the bumps and dips in the road surface. An independent rear suspension (IRS) features the rear wheels being independently sprung. In rear wheel driven vehicles, an IRS allows for a de-coupling of the differential from the axle thereby providing more room and lighter weight components. Even in front wheel drive vehicles, an IRS provides benefits, including controlling the camber angle for the rear tires during steering and braking.
One general type of IRS is referred to as a double wishbone suspension. This type of suspension is characterized by the presence of two sets of lateral “A” arms, typically called upper and lower control arms, and toe links. Each control arm has two attachments to the body and a single attachment to the wheel carrier or knuckle. The three knuckle attachments (upper arm, lower arm, toe link) on each side establish the plane of each wheel and control both camber angle and toe angle while reacting to wheel loads. Each side is separate from the other half which serves to independently isolate the reaction of each wheel to the road surface.
A more refined form of the double wishbone suspension is the multi-link suspension. This type of suspension conceptually separates the structural performance of each “A” arm into two tension/compression links. Thus, a 5-Link independent rear suspension can be thought of as separating the upper “A” arm into an “upper trailing link” and a “camber link”, separating the lower “A” arm into a “lower trailing link” and a “spring link”, and retaining a “toe link”. The orientation and length of each link governs the suspension's geometric performance as well as the magnitude of link loading when wheel forces are reacted. The spatial distribution of the link body attachments also dissipates wheel loads over a wider portion of the vehicle structure.
FIGS. 1A and 1B depict an example of an arrangement of the components of a prior art conventional 5-link IRS 10. The lower trailing link 12 and the upper trailing link 14 constitute the longitudinal linkages of the conventional 5-link IRS 10, wherein these linkages serve to locate the wheel longitudinally and react to tractive loads and brake torques. Note that the lower and upper trailing links 12, 14 are located within the envelope of the subframe rail 16, which has been curved in order to provide accommodation space for the upper trailing link. The camber link 18, the toe link 20 and the spring link 22, constitute that portion of the conventional 5-link IRS which establishes the wheel plane orientation and reacts to vertical and lateral loads. Also depicted are a spring 24 and strut 26 showing their general spatial interrelationship with respect to the 5-link IRS 10. Note that all the links are attached to the knuckle or wheel carrier denoted by node 30.
Conventional multi-link suspensions orient the forward upper and lower “trailing” links in a substantially lateral orientation. This practice results in body side attachments inboard of the longitudinal rails which requires routing the rail up over the upper trailing links. This body rail configuration increases the rail offset which degrades its structural efficiency and also reduces the interior compartment volume above the rail. Additionally, the suspension attachment structure that is packaged inboard of the body rails reduces the under floor package space for fuel, batteries, and/or exhaust. Attaching the trailing links inboard of the body rails at large plan view angular orientations also causes higher link axial loads when reacting to longitudinal suspension loads.
Accordingly, what remains needed in the art is an improved 5-link IRS system for motor vehicles which can better manage the reaction of suspension longitudinal loads while providing features which enhance the package space and weight characteristics over that possible in the current art of 5-link IRS systems.